1. Field of the Invention
This invention relates to a magnetic recording medium, and more particularly to a binder of the same.
2. Description of the Prior Art
Generally, in the manufacture of a magnetic tape, ferromagnetic powder, binder and, as the occasion demands, different agents are mixed with each other to prepare a magnetic paint, and then a non-magnetic substrate is coated with the prepared magnetic paint. A high molecular polybutadiene group resin having molecular weight of one hundred thousand, for example, butadiene-acrylonitrile copolymer or butadiene-styrene copolymer, blended with other resins is used for the binder. The high molecular polybutadiene group resin is effective to improve wear resistance of the magnetic tape and flexibility thereof at a lower temperature.
However, such a binder has the following defects:
(1) Since it does not have sufficient solubility for organic solvents, magnetic powder cannot be satisfactorily dispersed throughout it. PA0 (2) Since it has little possibility of crosslinking by chemical bond, the characteristics, particularly elastic modulus, of the magnetic tape deteriorate at high temperature and high humidity. The magnetic tape is apt to adhere to a guide drum, for example, in a video tape recorder, resulting in the deterioration of the tape running characteristics. That becomes a great problem for such apparatus in which the magnetic tape is put under various environmental conditions.